Here is a map of the workshop places (and here is an aerial photo version).
You may also wish to use these searchable interactive maps: map of Tallinn, map of Estonia, incl. Tallinn.
The city is 4 kms from the airport. You reach it by bus No. 2 or taxi.
The bus stop is by the door of the arrivals hall. The timetable is here. You are travelling in the direction of "Reisisadam", a good central stop is "A. Laikmaa" between Viru Center and Hotel Tallink. Tickets can be bought from the R-Kiosk in the arrivals hall (10 EEK) or from the driver (15 EEK).
The taxi situation in Tallinn is terrible, if you want that I put it mildly. It is always preferable to order a taxi by phone. In the city you should never take a taxi from the street, but you could consider a phone order even at the airport. Some reasonable companies are, e.g., Reval Takso (phone 621 2111), Marabu (phone 650 0006). The rates vary wildly (reasonable rates are 35..45 EEK initial fare + 7..8 EEK per km), but a taxi ride to the center should under no circumstances cost more than 200 EEK. Always request a printed receipt. Know that you have the right to choose any taxi from the line.
Both Taanilinna (Uus 6) and Meriton Old Town Hotel (Lai 49) are in the lower, merchant town part of the Old Town, thus very central. Taanilinna is close to Viru street, one of the main pedestrian streets. Meriton Old Town is at the end of the Lai street, just a few steps from Oleviste (St Olaf's) Church.
The Academy of Sciences (Kohtu 6) is on Toompea (the Dome Hill), quite close to Toomkirik (the Dome church). It is a dark gray-brick palace off the street inside a courtyard, squeezed between the Embassy of Finland and the Office of the Chancellor of Justice, which are bright yellow. From each hotel it is 15 mins walking, assuming you are walking in the right direction.
Our lunches will be at Olematu Rüütel (Kiriku põik 4a), which is as close to Toomkirik as the Academy of Sciences but in the opposite direction. Our dinner will be at Maikrahv (Raekoja plats 8), on the northern side of Raekoja plats (Town Hall square).
The Estonian currency, the kroon (crown), is pegged to the Euro at the rate of 1 EUR = 15.6466 EEK. ATMs abound in the city although they are not always well visible. Beware that an Estonian ATM first gives you your money and only then returns the card. Worse, you have to ask the machine to give your card back. Luckily for you, these machines speak English. Almost all businesses (but not newsstands, bus drivers, taxi drivers) accept bank cards (even for the smallest payments) and the local people carry very little cash.
The city is packed with public WiFi hotspots (some 350 in all Tallinn, whereof some 200 are in the center). In particular, you can connect yourself in any decent cafeteria or pub. More than a half of these hotspots are free (look out, e.g., for Reval Cafes), in others (those run by Elisa) you have to get a ticket by SMSing "wifi pilet" to 19131. The ticket (consisting in the username and password you receive in an instant reply) costs 10 EEK (charged to your mobile calls bill) and is valid for 24 hrs throughout the entire Elisa network. Check out this index of public WiFi hotspots in the country.
Normal European-style plug pins, 220 V/50 Hz. No headache about that.
Do realize that Estonia uses East-European Time (EET) which is 1 h ahead of CET.
For tourist information on Tallinn, check out the city's official tourism page or the witty, no-nonsense Tallinn guide of InYourPocket.
For in-depth background information on Estonia, we recommend the Estonian Institute's Estonica.